Now Ozzy's firing back, saying not only is Bill unhealthy, he's fat, too.

"I don't think he could have done the gig, to be honest. He's incredibly overweight," Osbourne told the NY Daily News. "A drummer has to be in shape. He's already had two heart attacks. I don't want to be responsible for his life."

Previously, Ozzy publicly questioned Bill's mental faculties, telling a British music magazine that during initial rehearsals for the reunion tour, Ward had a bunch of Post-It notes all over his drums. When Osbourne asked what they were for, Bill allegedly replied that he needed them to remember what he was doing.

“But he didn’t come clean and say, ‘I can’t cut this gig, but can we work something out, guys, where I’ll come on but with another drummer backing me up?’ Or, ‘I’ll come and play a few songs,’" Ozzy added. "That would have been cool.”

For his part, Ward maintains that it was always an "all or nothing" deal to him and he never considered doing it halfway. "I’m the drummer in Sabbath," he said, "and quite capable of doing the job.”